Lubricant additive and lubricant oil composition

ABSTRACT

A lubricant additive containing (A) a nitrogen-containing compound represented by the general formula (1) and (B) a borate ester compound represented by the general formula (2) and/or a borate ester compound represented by the general formula (3); and a lubricant oil composition containing the lubricant additive and a lubricant base oil, the lubricant additive and the lubricant oil composition containing an oiliness agent-type friction modifier that can exhibit a better friction reduction effect than that of conventional oiliness agent-type friction modifiers under a wider range of friction conditions.

TECHNICAL FIELD

The present invention relates to a lubricant additive and a lubricant oil composition. It specifically relates to a lubricant additive and a lubricant oil composition which show excellent friction reduction performance, and especially a lubricant oil composition which is suitable as a lubricant oil for drive systems such as an automatic transmission fluid (ATF) and a continuously various transmission fluid (CVT fluid) or as a fuel-saving lubricant oil for internal combustion engines.

BACKGROUND ART

Lubricant oils are used for internal combustion engines, automatic transmissions, bearings and the like to smooth their operations. Especially, automatic transmission fluids such as ATF and a belt-type continuously variable transmission fluid (CVT fluid) and lubricant oils for internal combustion engines (engine oils) are required to have higher performance due to high performance, high power, and severe operating conditions of the engines. Therefore, in order to meet the required performance, various additives such as an anti-wear agent, a metallic detergent, an ashless dispersant and an antioxidant are contained in the engine oils for example. Since quite complex friction properties are required in controlling the friction properties of the clutches of automatic transmissions, an additive to increase the friction coefficient and an additive to decrease the friction coefficient are also used in the automatic transmission fluids, with the temperature properties and durability thereof taken into account. In addition, since the internal combustion engines cause a large energy loss in a friction part which involves a lubricant oil, a friction modifier (hereinafter sometimes referred to as “FM”) to reduce friction is used especially in fuel-saving lubricant oils that pursue reduction of fuel consumption.

The additive generally used to reduce a friction coefficient is named FM. The FM used in internal combustion engine oils can be categorized into two types: molybdenum-based FMs which contain molybdenum; and oiliness agent-type FMs which improve oiliness to reduce friction.

Of these FMs, the molybdenum-based FMs have limitations in maintaining the favorable friction reduction effect for a long period by conventional techniques even though the FMs have an excellent friction reduction effect in their early stage of use. Since molybdenum dithiocarbamate (MoDTC) widely used in engine oils as the molybdenum-based FM contains ash and sulfur and molybdenum dithiophosphate (MoDTP) also widely used in engine oils as the molybdenum-based FM contains ash, sulfur, and phosphorus, they may negatively affect a exhaust gas purifier of internal combustion engines or may interfere in recycling the lubricant oils. Therefore, it is required to reduce the additive amount of molybdenum-based friction modifier.

On the other hand, the oiliness agent-type FMs such as ester-based, amine-based, and amide-based FMs can avoid the above problems of molybdenum-based FMs, and therefore the importance of the oiliness agent-type FMs is increasing in view of the environment. In addition, most of the FMs used in the lubricant oils for drive systems are the oiliness agent-type ones.

As such, it is now important to improve the friction reduction performance of the oiliness-based FMs.

As a technique related to such an oiliness agent-type friction modifier, Patent Document 1 for example discloses a lubricant oil composition containing a (thio)urea compound as an oiliness agent-type FM. Patent Document 2 discloses a lubricant oil composition containing a (thio)ureido compound as an oiliness agent-type FM. The lubricant oil compositions described in Patent Documents 1 and 2 are seen to be able to show better friction reduction performance than lubricant oil compositions containing a conventional oiliness agent-type FM.

CITATION LIST Patent Literature

-   Patent Document 1: Japanese Patent Application Laid-Open (JP-A) No.     2005-120242 -   Patent Document 2: JP-A No. 2005-120243

SUMMARY OF INVENTION Problems to be Solved by the Invention

Unadvantageously, the degree of the friction reduction effect of lubricant oil compositions containing the oiliness agent-type FM described in Patent Documents 1 or 2 can vary relatively largely, for example depending on the sliding speed. A rotation speed of an internal combustion engine can vary in a wide range, 600 to 800 rpm for example, depending on the operation conditions. Therefore, when such lubricant oil compositions containing the oiliness agent-type FMs are used as engine oils or automatic transmission fluids, they may be inferior to lubricant oil compositions containing molybdenum-based FMs in terms of the friction reduction effect, depending on the conditions of use.

In view of the above, an object of the present invention is to provide a lubricant additive and a lubricant oil composition which contain an oiliness agent-type friction modifier capable of exhibiting a better friction reduction effect than that of conventional oiliness agent-type friction modifiers under a wider range of friction conditions. The present invention also provides a lubricant oil composition especially suitable as an automatic transmission fluid or a lubricant oil for internal combustion engines.

Means for Solving the Problems

In order to solve the above problem, the present invention has the following aspects.

A first aspect of the present invention is a lubricant additive having:

(A) a nitrogen-containing compound represented by the general formula (1); and

(B) a borate ester compound represented by the general formula (2) and/or a borate ester compound represented by the general formula (3).

(In the formula (1), R¹ represents a hydrocarbyl group having a carbon number of 1 to 30 or a functionalized hydrocarbyl group having a carbon number of 1 to 30; each of R², R³, and R⁴ independently represents a hydrocarbyl group having a carbon number of 1 to 30, a functionalized hydrocarbyl group having a carbon number of 1 to 30, or a hydrogen atom; m represents an integer of 0 or 1; and n represents an integer of 0 or 1 where m is 1.)

(In the formula (2), R⁵ represents a hydrocarbyl group having a carbon number of 1 to 30 or a functionalized hydrocarbyl group having a carbon number of 1 to 30; each of R⁶ and R⁷ independently represents a hydrocarbyl group having a carbon number of 1 to 30, a functionalized hydrocarbyl group having a carbon number of 1 to 30, or a hydrogen atom.)

(In the formula (3), R⁸ represents a hydrocarbyl group having a carbon number of 1 to 30 or a functionalized hydrocarbyl group having a carbon number of 1 to 30; each of R⁹ and R¹⁰ independently represents a hydrocarbyl group having a carbon number of 1 to 30, a functionalized hydrocarbyl group having a carbon number of 1 to 30, or a hydrogen atom.)

In the present invention, the “functionalized hydrocarbyl group” refers to a hydrocarbyl group modified to contain oxygen, nitrogen, sulfur, phosphorus, etc. Non-limited examples include hydrocarbyl groups derived from esters, carboxylic acids, ethers, amides, amines, etc.

In the first aspect of the present invention, a molar ratio of the molar content of the component (B) in terms of boron to the molar content of the component (A) is no less than 0.05 and no more than 4.0.

In the present invention, the “component (A)” refers to the aforementioned “nitrogen-containing compound represented by the general formula (1)”. The “component (B)” refers to the aforementioned “borate ester compound represented by the general formula (2) and/or the borate ester compound represented by the general formula (3)”. The “molar content of the component (B) in terms of boron” refers to a molar amount of the component (B) determined in terms of the boron content. That is, one mole of the borate ester compound represented by the general formula (2) is equivalent to one mole of the component (B) in terms of boron; and one mole of the borate ester compound represented by the general formula (3) is equivalent to three moles of the component (B) in terms of boron. The “molar ratio of the molar content of the component (B) in terms of boron to the molar content of the component (A)” refers to a molar ratio calculated by the division, (molar content of the component (B) in terms of boron)/(molar content of the component (A)). Herein, when the component (A) includes a plurality of compounds, the molar content of the component (A) is a sum of the molar contents of all the compounds included in the component (A). In addition, when the component (B) includes a plurality of compounds, the molar amount of the component (B) is a sum of the molar contents in terms of boron of all the compounds included in the component (B).

The lubricant additive according to the first aspect of the present invention may further contain one or more selected from: a lubricant base oil, an ashless dispersant, an antioxidant, a friction modifier, an anti-wear agent, a metallic detergent, a viscosity index improver, a corrosion inhibitor, an anti-rust agent, an anti-emulsifier, a metal deactivator, a defoaming agent, and a coloring agent.

A second aspect of the present invention is a lubricant oil composition containing a lubricant base oil and the lubricant additive according to the first aspect of the present invention.

In the present invention, the “automatic transmission” refers to a transmission which has a function to automatically change transmission gear ratios. It is not limited to conventional automatic transmissions (AT) exemplified by torque converter-type ones having a combination of a torque converter and a multistage transmission. It also includes a continuously variable transmission which can continuously change transmission gear ratios steplessly (CVT: belt-, chain-, toroidal-type ones, for example).

Effects of the Invention

The lubricant additive according to the first aspect of the present invention contains both the component (A) and the component (B). The first aspect of the present invention can provide a lubricant additive containing an oiliness agent-type friction modifier which can exhibit a better friction reduction effect than that of conventional oiliness agent-type friction modifiers under a wider range of friction conditions.

The lubricant oil composition of the second aspect of the present invention contains the lubricant additive according to the first aspect of the present invention. Therefore, the second aspect of the present invention can provide a lubricant oil composition containing an oiliness agent-type friction modifier which can exhibit a better friction reduction effect under a wider range of friction conditions than lubricant oil compositions containing a conventional oiliness agent-type friction modifier.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph showing comparison between the test result of Example 1 and the test results of Comparative Examples.

FIG. 2 is a graph showing comparison between the test result of Example 3 and the test results of Comparative Examples.

FIG. 3 is a graph showing comparison between the test result of Example 2 and the test results of Comparative Examples.

FIG. 4 is a graph showing comparison between the test results of Examples 1, 4, and 5, and the test result of Comparative Example 1.

FIG. 5 is a graph showing the test results of Examples 1 and 6 to 8.

MODES FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail.

1. Lubricant Additive

The lubricant additive according to the first aspect of the present invention will be described.

<Component (A)>

The component (A) in the present invention is a nitrogen-containing compound represented by the general formula (1).

In the general formula (1), m is an integer of 0 or 1; and n is an integer of 0 or 1 where m is 1. n is preferably 0.

In the general formula (1), R¹ is a hydrocarbyl group having a carbon number of 1 to 30 or a functionalized hydrocarbyl group having a carbon number of 1 to 30, and is preferably a hydrocarbyl group having a carbon number of 10 to 30 or a functionalized hydrocarbyl group having a carbon number of 10 to 30.

Herein, specific examples of the hydrocarbyl group described above include alkyl groups, cycloalkyl groups, alkylcycloalkyl groups, alkenyl groups, aryl groups, alkylaryl groups, and arylalkyl groups.

Examples of the alkyl groups include methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl.

Examples of the cycloalkyl groups are those having a carbon number of 5 to 7, such as cyclopentyl, cyclohexyl, and cycloheptyl.

Examples of the alkylcycloalkyl groups are those having a carbon number of 6 to 30, such as methylcyclopentyl, dimethylcyclopentyl, methylethylcyclopentyl, diethylcyclopentyl, methylcyclohexyl, dimethylcyclohexyl, methylethylcyclohexyl, diethylcyclohexyl, methylcycloheptyl, dimethylcycloheptyl, methylethylcycloheptyl, and diethylcycloheptyl (substitution of the alkyl groups on the cycloalkyl groups may be at any position.)

Examples of the alkenyl groups include butenyl, pentenyl, hexenyl, heptenyl, octenyl, nonenyl, decenyl, undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl, hexadecenyl, heptadecenyl, and octadecenyl (the double bond may be at any position.)

Examples of the aryl groups include phenyl and naphthyl.

Examples of the alkylaryl groups are those having a carbon number of 7 to 30, such as tolyl, xylyl, ethylphenyl, propylphenyl, butylphenyl, pentylphenyl, hexylphenyl, heptylphenyl, octylphenyl, nonylphenyl, decylphenyl, undecylphenyl, and dodecylphenyl (the alkyl groups are preferably linear; substitution on the aryl groups may be at any position but preferably in the para position.)

Examples of the arylalkyl groups include those having a carbon number of 7 to 30, such as benzyl, phenylethyl, phenylpropyl, phenylbutyl, phenylpentyl, and phenylhexyl (the alkyl groups are preferably linear; substitution on the alkyl groups may be at any position but preferably in the co-position (the chain end opposite to the α-position).

The hydrocarbyl group of R¹ described above is preferably an alkyl group or an alkenyl group. R¹ is more preferably an alkyl group or alkenyl group having a carbon number of 12 to 24 or a functionalized alkyl group or alkenyl group having a carbon number of 12 to 24, and especially preferably an alkenyl group having a carbon number of 12 to 24. When R¹ is an alkenyl group, alkyl group(s) which sandwiches the double bond is preferably linear. Further, when n is 1 in the general formula (1), the carbon number of R¹ is preferably no less than 16, in view of improving the solubility into a base oil.

In addition, when R¹ is an alkyl group, it is preferably linear. However, in view of making it easy to use under low-temperature conditions, R¹ is more preferably an alkyl group having a methyl group at the α-position of the N—(C═O)_(n)-group in the general formula (1). This is because when R¹ is an alkyl group having such a structure, it is possible to lower the freezing point compared with the case in which R¹ is a completely linear alkyl group.

In the general formula (1), each of R², R³, and R⁴ independently represents a hydrocarbyl group having a carbon number of 1 to 30, a functionalized hydrocarbyl group having a carbon number of 1 to 30, or a hydrogen atom. It is preferable that at least one of R³ and R⁴ is a hydrogen atom, and it is more preferable that both R³ and R⁴ are hydrogen atoms. Having R³ and/or R⁴ as a hydrogen atom allows increase in the adsorbability onto a friction face and therefore enables the friction reduction effect to be improved easily.

Preferred examples of the nitrogen-containing compound represented by the general formula (1) are urea compounds having a hydrocarbyl group with a carbon number of 1 to 30 or a fuctionalized hydrocarbyl group with a carbon number of 1 to 30 when m is 1 and n is 0 for example.

Such urea compounds may be synthesized by a known synthesis method without particular limitations. For example, a method of synthesis by the reaction between an isocyanate compound and ammonia or an amine compound represented by the below formula (4) may be adopted.

Herein, a known isocyanate compound may be employed as the isocyanate compound in the above general formula (4), without particular limitations. Examples of the isocyanate compound that can be used for the reaction represented by the general formula (4) include: isocyanate compounds in which R¹ is a hydrocarbyl group having a carbon number of 1 to 30 or a functionalized hydrocarbyl group having a carbon number of 1 to 30; preferably isocyanate compounds in which R¹ is a hydrocarbyl group having a carbon number of 10 to 30 or a functionalized hydrocarbyl group having a carbon number of 10 to 30; more preferably isocyanate compounds in which R¹ is an alkyl group or alkenyl group having a carbon number of 12 to 24 or a functionalized hydrocarbyl group having a carbon number of 12 to 24; and especially preferably isocyanate compounds having an alkenyl group with a carbon number of 12 to 24.

In the reaction represented by the above general formula (4), a known primary or secondary amine compound or ammonia can be used as a nucleophilic reagent without particular limitations. Examples of the primary or secondary amine compound that can be used for the reaction represented by the above general formula (4) include: amine compounds having a hydrocarbyl group with a carbon number of 1 to 30 or a functionalized hydrocarbyl group with a carbon number of 1 to 30; preferably amine compounds having a hydrocarbyl group with a carbon number of 1 to 10; and more preferably amine compounds having a hydrocarbyl group with a carbon number of 1 to 4.

More preferred specific examples of the nitrogen-containing compound represented by the general formula (1) are urea compounds having at least one alkyl group or alkenyl group with a carbon number of 12 to 24, such as dodecyl urea, tridecyl urea, tetradecyl urea, pentadecyl urea, hexadecyl urea, heptadecyl urea, octadecyl urea, oleyl urea, and stearyl urea.

Other preferred examples of the nitrogen-containing compound represented by the general formula (1) are ureido compounds having a hydrocarbyl group with a carbon number of 1 to 30 or a functionalized hydrocarbyl group with a carbon number of 1 to 30 when m is 1 and n is 1 for example.

The ureido compounds described above may be synthesized by a known synthesis method without particular limitations. For example, a method of synthesis by the reaction between an acid chloride and urea or a urea compound represented by the below general formula (5) may be employed.

A known acid chloride may be employed as the acid chloride in the reaction represented by the above general formula (5), without particular limitations. Examples of the acid chloride that can be used in the reaction represented by the general formula (5) include: carboxylic acid chlorides in which R¹ is a hydrocarbyl group having a carbon number of 1 to 30 or a functionalized hydrocarbyl group having a carbon number of 1 to 30; preferably carboxylic acid chlorides in which R¹ is a hydrocarbyl group having a carbon number of 10 to 30 or a functionalized hydrocarbyl group having a carbon number of 10 to 30; more preferably carboxylic acid chlorides in which R¹ is an alkyl group or alkenyl group having a carbon number of 10 to 24 or a functionalized hydrocarbyl group having a carbon number of 10 to 24; and especially preferably carboxylic acid chlorides in which R¹ is an alkenyl group having a carbon number of 12 to 24.

A known urea compound may be employed as the urea compound in the reaction represented by the above general formula (5), without particular limitations. Examples of the urea compound that can be used in the reaction represented by the general formula (5) include urea, N-methyl urea, N-ethyl urea, N-tert-butyl urea, and N,N′-dimethyl urea. These urea compounds can be produced by a known synthesis method such as reaction between an isocyanate and ammonia or an amine compound.

Other preferred examples of the nitrogen-containing compound represented by the general formula (1) are amide compounds having a hydrocarbyl group with a carbon number of 1 to 30 or a functionalized hydrocarbyl group with a carbon number of 1 to 30 when m is 0 for example.

The amide compounds described above may be synthesized by a known synthesis method without particular limitations.

The content of the component (A) in the lubricant additive of the present invention is not particularly limited. For example, it may be such an amount that can realize the usual or preferable content of the component (A) in the lubricant oil composition of the present invention described below.

<Component (B)>

The component (B) in the present invention is a borate ester compound represented by the general formula (2) below or a borate ester compound represented by the general formula (3) below, or a mixture thereof.

(In the formula (2), R⁵ represents a hydrocarbyl group having a carbon number of 1 to 30 or a functionalized hydrocarbyl group having a carbon number of 1 to 30; each of R⁶ and R⁷ independently represents a hydrocarbyl group having a carbon number of 1 to 30, a functionalized hydrocarbyl group having a carbon number of 1 to 30, or a hydrogen atom.)

(In the formula (3), R⁸ represents a hydrocarbyl group having a carbon number of 1 to 30 or a functionalized hydrocarbyl group having a carbon number of 1 to 30; each of R⁹ and R¹⁰ independently represents a hydrocarbyl group having a carbon number of 1 to 30, a functionalized hydrocarbyl group having a carbon number of 1 to 30, or a hydrogen atom.)

Both the borate ester compound represented by the general formula (2) and the borate ester compound represented by the general formula (3) can be the component (B) in the present invention. The borate ester compound represented by the general formula (2), though, is more preferred. As mentioned above, the borate ester compound represented by the general formula (2) and the borate ester compound represented by the general formula (3) may be used in combination.

The hydrocarbyl group having a carbon number of 1 to 30 in the general formulas (2) and (3) above is preferably an alkyl group or alkenyl group having a carbon number of 1 to 30, and more preferably an alkyl group having a carbon number of 1 to 30. The carbon number is preferably no less than 3, more preferably no less than 8, and still more preferably no less than 12, and it is preferably no more than 24.

The borate ester represented by the general formula (2) can be produced for example by reacting an alcohol having the hydrocarbyl group with a carbon number of 1 to 30 described above with orthoboric acid (H₃BO₃) at a molar ratio of 3:1.

The borate ester represented by the general formula (3) can be produced for example by reacting an alcohol having the hydrocarbyl group with a carbon number of 1 to 30 described above with orthoboric acid (H₃BO₃) at a molar ratio of 1:1.

The reaction conditions for the synthesis of the borate ester are not particularly limited. Usually, the reaction temperature is especially preferably no less than 100° C., which makes it possible to simultaneously remove moisture produced with the progress of the reaction.

Preferred examples of the component (B) specifically include triethyl borate, tri-n-propyl borate, triisopropyl borate, tri-n-butyl borate, tri-sec-butyl borate, tri-tert-butyl borate, trihexyl borate, trioctyl borate, tridecyl borate, tridodecyl borate, trihexadecyl borate, trioctadecyl borate, triphenyl borate, tribenzyl borate, triphenethyl borate, tritolyl borate, tri(ethylphenyl)borate, tri(propylphenyl)borate, tri(butylphenyl)borate, and tri(nonylphenyl)borate. Among them, tri-n-butyl borate, trioctyl borate, tridodecyl borate and so on are especially preferred.

The content of the component (B) in the lubricant additive of the present invention is not particularly limited. For example, it may be such an amount that can realize the usual or preferable content of the component (B) in the lubricant oil composition of the present invention described below.

In the lubricant additive of the present invention and in the lubricant oil composition of the present invention described below, a molar ratio of the molar content of the component (B) in terms of boron to the molar content of the component (A) ((the molar content of the component (B) in terms of boron)/(the molar content of the component (A))) is preferably no more than 4, more preferably no more than 3.5, and still more preferably no more than 3. It is preferably no less than 0.05, more preferably no less than 0.1, still more preferably no less than 0.5, and especially preferably no less than 1.

As noted above, the “molar content of the component (B) in terms of boron” refers to a molar amount of the component (B) determined in terms of the boron content. That is, one mole of the borate ester compound represented by the general formula (2) is equivalent to one mole of the component (B) in terms of boron; and one mole of the borate ester compound represented by the general formula (3) is equivalent to three moles of the component (B) in terms of boron.

Even when the component (A) and/or the component (B) includes two or more different compounds, a preferred molar ratio between the molar content of the component (A) and the molar content of the component (B) in terms of boron is the same as the ratio described above. Herein, when the component (A) includes two or more compounds, the molar content of the component (A) is a sum of the molar contents of all the compounds included in the component (A). When the component (B) includes two or more compounds, the molar content of the component (B) in terms of boron is a sum of the molar contents in terms of boron of all the compounds included in the component (B).

With the above preferable range of the molar ratio of the molar content of the component (B) in terms of boron to the molar content of the component (A), the friction reduction effect of the lubricant additive and the lubricant oil composition of the present invention can be further improved.

The lubricant additive of the present invention and the lubricant oil composition of the present invention described below preferably further contain at least one selected from (C) an ashless dispersant, (D) an antioxidant, and (E) an anti-wear agent containing phosphorus.

<Component (C)>

A known ashless dispersant that can be contained in lubricant oil compositions may be employed as (C) the ashless dispersant, without particular limitations. Examples of the compound that can be used as the component (C) include: nitrogen-containing compounds having at least one linear or branched alkyl group or alkenyl group with a carbon number of 40 to 400 in the molecule, or derivatives thereof; and modified products of alkenyl succiniimide (for example, boric acid-modified products, sulfur compound-modified products, acylation-modified products). One or more compounds randomly selected from these may be contained.

The carbon number of the alkyl group or the alkenyl group is no less than 40, preferably no less than 60; and it is no more than 400, preferably no more than 350. When the carbon number of the alkyl group or the alkenyl group is less than 40, the solubility of the compound into a lubricant base oil degrades. On the other hand, when the carbon number of the alkyl group or the alkenyl group is greater than 400, the low-temperature fluidity of the lubricating oil composition deteriorates. Thus, both cases are unfavorable. The alkyl group or the alkenyl group may be linear or branched. Preferred examples of the alkyl group and the alkenyl group specifically include: branched alkyl groups and branched alkenyl groups derived from an oligomer of an olefin such as propylene, 1-butene, and isobutylene, or from a co-oligomer of a plurality of olefins such as a co-oligomer of ethylene and propylene.

When the component (C) is contained in the lubricant additive of the present invention, the content thereof is preferably such an amount that can realize the usual or preferable content of the component (C) in the lubricant oil composition of the present invention described below.

<Component (D)>

A known antioxidant that can be used in lubricant oil compositions, such as a phenol-based antioxidant, amine-based antioxidant, and a metallic antioxidant, may be employed as (D) the antioxidant, without particular limitations. Adding the antioxidant enables further improvement of the anti-oxidation properties of the lubricant oil composition, and therefore enables further improvements of the base number retention and the high-temperature detergency of the lubricant additive of the present invention and the lubricant oil composition of the present invention described below.

Preferred examples of the phenol-based antioxidant include: 4,4′-methylenebis(2,6-di-tert-butylphenol);

-   4,4′-bis(2,6-di-tert-butylphenol); -   4,4′-bis(2-methyl-6-tert-butylphenol); -   2,2′-methylenebis(4-ethyl-6-tert-butylphenol); -   2,2′-methylenebis(4-methyl-6-tert-butylphenol); -   4,4′-butylidenebis(3-methyl-6-tert-butylphenol); -   4,4′-isopropylidenebis(2,6-di-tert-butylphenol); -   2,2′-methylenebis(4-methyl-6-nonylphenol); -   2,2′-isobutylidenebis(4,6-dimethylphenol); -   2,2′-methylenebis(4-methyl-6-cyclohexylphenol); -   2,6-di-tert-butyl-4-methylphenol; -   2,6-di-tert-butyl-4-ethylphenol; -   2,4-dimethyl-6-tert-butylphenol; -   2,6-di-tert-butyl-α-dimethylamino-p-cresol; -   2,6-di-tert-butyl-4-(N,N-dimethylaminomethyl)phenol; -   4,4′-thiobis(2-methyl-6-tert-butylphenol); -   4,4′-thiobis(3-methyl-6-tert-butylphenol); -   2,2′-thiobis(4-methyl-6-tert-butylphenol); -   bis(3-methyl-4-hydroxy-5-tert-butylbenzyl)sulfide; -   bis(3,5-di-tert-butyl-4-hydroxybenzyl)sulfide; -   2,2′-thio-diethylenebis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)     propionate]; -   tridecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;     pentaerythrityl-tetrakis[3-(3,5-di-ter-butyl-4-hydroxyphenyl)     propionate]; -   octyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate;     octadecyl-3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate; -   octyl-3-(3-methyl-5-tert-butyl-4-hydroxyphenyl)propionate.     Two or more of these may be used in combination.

Examples of the amine-based antioxidant include: phenyl-α-naphthyl amine; alkylphenyl-α-naphthyl amine; and di(alkylphenyl)amine. Two or more of these may be used in combination.

The phenol-based antioxidants and the amine-based antioxidants exemplified above may be contained in combination.

When the component (D) is contained in the lubricant additive of the present invention, the content thereof is preferably such an amount that can realize the usual or preferable content of the component (D) in the lubricant oil composition of the present invention described below.

<Component (E)>

Preferred examples of (E) the anti-wear agent containing phosphorus include phosphorous acid esters, phosphoric acid esters, metal salts and amine salts of phosphorous acid esters, and metal salts and amine salts of phosphoric acid esters. Examples of the phosphorus compound that can be employed as the component (E) include phosphorous acid monoester, monothiophosphorous acid monoester, dithiophosphorous acid monoester, trithiophosphorous acid monoester, phosphorous acid diester, monothiophosphorous acid diester, dithiophosphorous acid diester, trithiophosphorous acid diester, phosphoric acid monoester, monothiophosphoric acid monoester, dithiophosphoric acid monoester, trithiophosphoric acid monoester, phosphoric acid diester, monothiophosphoric acid diester, dithiophosphoric acid diester, trithiophosphoric acid diester, phosphonic acid monoester, monothiophosphonic acid monoester, and dithiophosphonic acid monoester.

Examples of the metal salt of the phosphorus compound that can be used as the component (E) include metal salts produced by reaction of a metal base such as a metal chloride, a metal hydroxide, and a metal oxide with the above phosphorus compound.

A hydrocarbon group of the compound of the component (E) may have any possible linear structure and branched structure. A position of a double bond in an alkenyl group, a bonding position of an alkyl group to a cycloalkyl group, a bonding position of an alkyl group to an aryl group, and a bonding position of an aryl group to an alkyl group may also be any position possible. The hydrocarbon group may also have a (poly) alkylene oxide group such as a (poly) ethylene oxide group and a (poly)propylene oxide group.

Preferred specific examples of the component (E) include: phosphorus compounds having a primary, secondary, or tertiary alkyl group with a carbon number of 3 to 24, preferably a carbon number of 4 to 18, and especially preferably a carbon number of 4 to 12; and metal salts and amine salts thereof.

Herein, the metals of the metal salts are not particularly limited. Examples thereof include alkali metals such as lithium, sodium, potassium, and cesium; alkaline earth metals such as calcium, magnesium, and barium; and heavy metals such as zinc, copper, iron, lead, nickel, silver, manganese, and molybdenum. Among them, the alkaline earth metals such as calcium and magnesium, and zinc are preferred, and zinc is most preferred.

Specific examples of the amine compounds of the amine salts are ammonia, monoamine, diamine, and polyamine. More specifically, preferred examples thereof include aliphatic amines having an alkyl group or alkenyl group with a carbon number of 10 to 20, such as decylamine, dodecylamine, dimethyldodecylamine, tridecylamine, heptadecylamine, octadecylamine, oleylamine, and stearylamine (they may be linear or branched).

When the component (E) is contained in the lubricant additive of the present invention, the content thereof is not particularly limited. For example, it may be such an amount that can realize the usual or preferable content of the component (E) in the lubricant oil composition of the present invention described below.

2. Lubricant Oil Composition

The lubricant oil composition according to the second aspect of the present invention will be described. The lubricant oil composition of the present invention contains at least a lubricant base oil and the lubricant additive according to the first aspect of the present invention described above.

<Lubricant Base Oil>

A mineral base oil and/or a synthetic base oil used in ordinary lubricant oils may be employed as the lubricant base oil in the lubricant oil composition of the present invention, without particular limitations.

Specific examples of the mineral base oil include: those that are obtained by refining a lubricant oil fraction produced by vacuum-distilling a topped crude resulting from atmospheric distillation of a crude oil, through one or more treatment(s) such as solvent deasphalting, solvent extraction, hydrocracking, solvent dewaxing, and hydrorefining; wax-isomerized mineral oils; and lubricant base oils obtained by isomerizing GTL wax (gas-to-liquid wax) produced by Fischer-Tropsch process, etc.

The total aromatic content of the mineral base oil is not particularly limited. Preferably it is no more than 15 mass %, more preferably no more than 10 mass %, still more preferably no more than 6 mass %, still more preferably no more than 3 mass %, and especially preferably no more than 2 mass %, based on the total amount of the base oil as 100 mass %.

The total aromatic content is most preferably 0 mass %. When the total aromatic content of the base oil is greater than 15 mass %, the oxidation stability degrades, which is thus unfavorable.

Herein, the total aromatic content means an aromatic fraction content measured in accordance with ASTM D2549. Usually, the aromatic fraction includes alkylbenzene, alkylnaphthalenes, anthracene, phenanthrene, alkylated products thereof, compounds in which four or more benzene rings are condensed, and heteroaromatic compounds such as pyridines, quinolines, phenols, and naphthols.

The sulfur content of the mineral base oil is not particularly limited. Preferably, it is no more than 0.05 mass %, more preferably no more than 0.01 mass %, and especially preferably no more than 0.001 mass %. A lubricant oil composition with low sulfur content and better long-drain performance can be obtained by reducing the sulfur content of the mineral base oil.

Examples of the synthetic lubricant oil include: poly-α-olefins such as 1-octene oligomer and 1-decene oligomer, or hydrogenated products thereof; isobutene oligomer or hydrogenated products thereof; paraffin; alkylbenzenes; alkylnaphthalenes; diesters (ditridecyl glutalate, di-2-ethylhexyl adipate, diisodecyl adipate, ditridecyl adipate, di-2-ethylhexyl sebacate, etc.); polyol esters (trimethylolpropane caprylate, trimethylolpropane pelargonate, pentaerythritol-2-ethylhexanoate, pentaerythritolpelargonate, etc.); polyoxyalkylene glycol; dialkyldiphenyl ether; and polyphenyl ether.

Examples also include aromatic synthetic oils such as alkylnaphthalenes, alkylbenzenes, and aromatic esters, and mixtures thereof. Among them, poly-α-olefins are preferred. Typical examples of the poly-α-olefins are oligomers or co-oligomers of α-olefins having a carbon number of 2 to 32, preferably a carbon number of 6 to 16 (1-octene oligomer, decene oligomer, ethylene-propylene co-oligomer, etc.), and hydrogenated products of them.

In the lubricant oil composition of the present invention, the mineral base oil, the synthetic base oil, or any mixture of two or more selected from them may be used as the lubricant base oil. For example, one or more mineral base oil (s), one or more synthetic base oil(s), a mixed oil of one or more mineral base oil(s) and one or more synthetic base oil(s) may be used.

The kinematic viscosity of the lubricant base oil is not particularly limited. Preferably, the kinematic viscosity at 100° C. of the lubricant base oil is no more than 20 mm²/s, and more preferably no more than 10 mm²/s. On the other hand, the kinematic viscosity at 100° C. of the lubricant base oil is preferably no less than 1 mm²/s, and more preferably no less than 2 mm²/s. When the kinematic viscosity at 100° C. of the lubricant base oil is greater than 20 mm²/s, the low-temperature viscosity properties degrade. On the other hand, when the kinematic viscosity at 100° C. of the lubricant base oil is less than 1 mm²/s, the lubricity in an area to be lubricated degrades due to insufficient oil layer formation thereat, and the evaporation loss of the lubricant base oil increases. Neither of the cases is thus favorable.

Although the amount of evaporation loss of the lubricant base oil is not particularly limited, it is preferably no more than 20 mass %, more preferably no more than 16 mass %, and especially preferably no more than 10 mass %, in terms of NOACK volatility. When the NOACK volatility of the lubricant base oil is greater than 20 mass %, not only does the evaporation loss of the lubricant oil increase but also a sulfur compound, a phosphorus compound, or a metal component in the composition is likely to accumulate in an exhaust gas purifying device together with the lubricant base oil, resulting in increase in the oil consumption and likely causing negative influence on the performance of the exhaust gas purifying device. It is therefore unfavorable. The “NOACK volatility” herein is an evaporation loss of the lubricant oil measured in accordance with ASTM D5800.

Although the viscosity index of the lubricant base oil is not particularly limited, it is preferably no less than 80, more preferably no less than 100, and especially preferably no less than 120, in view of exhibiting excellent viscosity characteristics ranging from low temperature to high temperature. The upper limit of the viscosity index is not particularly limited. It is allowed to use: those having a viscosity index of about 135 to 180 such as normal paraffins, slack waxes, GTL waxes, and iso-paraffinic mineral oils obtained by isomerizing these; and those having a viscosity index of about 150 to 250 such as complex ester base oils and HVI-PAO base oils. When the viscosity index of the lubricant base oil is less than 80, the low-temperature viscosity properties deteriorate, which is thus unfavorable.

<Component (A)>

The content of the component (A) in the lubricant oil composition of the present invention is not particularly limited. However, based on the total amount of the composition, that is, based on the total amount of the lubricant oil composition as 100 mass %, the content of the component (A) is usually no less than 0.001 mass %, preferably no less than 0.01 mass %, and especially preferably no less than 0.1 mass %. It is usually no more than 5 mass %, preferably no more than 3 mass %, and especially preferably no more than 1.5 mass %. When the content of the component (A) is less than 0.001 mass %, the friction reduction effect may be insufficient. When it is greater than 5 mass %, the solubility may suffer a problem.

<Component (B)>

The content of the component (B) in the lubricant oil composition of the present invention is not particularly limited. However, based on the total amount of the composition, that is, based on the total amount of the lubricant oil composition as 100 mass %, the content of the component (B) is usually no less than 0.001 mass %, preferably no less than 0.01 mass %, and especially preferably no less than 0.1 mass %. It is usually no more than 5 mass %, preferably no more than 3 mass %, and especially preferably no more than 1.5 mass %. When the content of the component (B) is less than 0.001 mass %, the friction reduction effect may be insufficient. When it is greater than 5 mass %, the solubility may suffer a problem.

Since the lubricant oil composition of the present invention contains both the component (A) and the component (B) as a result of containing the lubricant additive of the present invention, it is possible to provide a lubricant oil composition containing an oiliness agent-type friction modifier which can show a better friction reduction effect under a wider range of friction conditions than lubricant oil compositions containing a conventional oiliness agent-type friction modifier. The anti-wear properties can also be improved.

In the present invention, a molar ratio of the molar content of the component (B) in terms of boron to the molar content of the component (A) ((the molar content of the component (B) in terms of boron)/(the molar content of the component (A))) is preferably no more than 4, more preferably no more than 3.5, and still more preferably no more than 3, as noted above. It is preferably no less than 0.05, more preferably no less than 0.1, still more preferably no less than 0.5, and especially preferably no less than 1.

With the molar ratio of the molar content of the component (B) in terms of boron to the molar content of the component (A) in the preferable range described above, the friction reduction effect of the lubricant oil composition of the present invention can be further improved.

<components (C), (D), and (E)>

The lubricant oil composition of the present invention preferably further contains at least one selected from (C) an ashless dispersant, (D) an antioxidant, and (E) an anti-wear agent containing phosphorus, in addition to the component (A) and the component (B), as mentioned above.

When the component (C) is contained in the lubricant oil composition of the present invention, the content thereof is usually no less than 0.01 mass % and preferably no less than 0.1 mass %, based on the total amount of the lubricant oil composition, that is, based on the total amount of the lubricant oil composition as 100 mass %. In addition, it is usually no more than 20 mass % and preferably no more than 10 mass %. When the content of the component (C) is less than 0.01 mass %, the effect of contributing to the base number retention under a high-temperature environment is likely to be insufficient. On the other hand, when the content of the component (C) is greater than 20 mass %, the low-temperature fluidity of the lubricant oil composition is likely to deteriorate greatly. Therefore, neither of the cases is favorable.

When the component (D) is contained in the lubricant oil composition of the present invention, the content thereof is usually no more than 5.0 mass %, preferably no more than 3.0 mass %, and still more preferably no more than 2.5 mass %, based on the total amount of the lubricant oil composition, that is, based on the total amount of the lubricant oil composition as 100 mass %. When the content of the component (D) is greater than 5.0 mass %, sufficient antioxidant properties proportional to the content may not be ensured, which is thus unfavorable. On the other hand, the content of the component (D) is preferably no less than 0.1 mass % and more preferably no less than 1 mass %, based on the total amount of the lubricant oil composition.

When the component (E) is contained in the lubricant oil composition of the present invention, the content thereof is not particularly limited. Usually it is no less than 0.1 mass % and no more than 5 mass %, based on the total amount of the composition, that is, based on the total amount of the lubricant oil composition as 100 mass %.

When the lubricant oil composition of the present invention is used as a lubricant oil for internal combustion engines, the content of the component (E) based on the total amount of the composition is preferably no less than 0.005 mass % and preferably no more than 0.08 mass % in terms of phosphorus, in order to reduce the burden on an exhaust-gas purifier.

When the lubricant oil composition of the present invention is used as a lubricant oil for automatic transmissions, the content of the component (E) based on the total amount of the composition is preferably no less than 0.005 mass % and more preferably no less than 0.01 mass % in terms of phosphorus. In addition, it is preferably no more than 0.1 mass %, more preferably no more than 0.05 mass %, and still more preferably no more than 0.03 mass % in terms of phosphorus.

When the content of the component (E) is too small, the anti-wear properties are likely to be insufficient. When the content of the component (E) is too large, an exhaust gas purifier or a sealing material of a device (e.g. an internal combustion engine, an automatic transmission) may be negatively affected. The reason why the preferable upper limit of the content of the phosphorus compound differs between the lubricant oil for internal combustion engines and the lubricant oil for automatic transmissions is that the lubricant oil for internal combustion engines contains more amount of the metallic detergent described below and that the negative influence on the sealing material is reduced by the effect of the metallic detergent.

The lubricant oil composition of the present invention may contain a known additive that can be used in lubricant oils depending on the purpose of use in order to further improve the performance of the lubricant oil composition. Examples of the additive include: (F) a friction modifier other than that of the present invention; (G) an anti-wear agent other than the component (E); (H) a metallic detergent; (I) a viscosity index improver; (J) a corrosion inhibitor; (K) an anti-rust agent; (L) an anti-emulsifier; (M) a metal deactivator; (N) a defoaming agent; and (O) a coloring agent.

The additive components (F) to (O) may also be contained in the lubricant additive according to the first aspect of the present invention described above.

<Component (F)>

A compound known as a friction modifier for lubricant oils can be used as the friction modifier other than the components (A) and (B), without particular limitations. Examples include: oiliness agent-type friction modifiers having, in the molecule, at least one alkyl group or alkenyl group with a carbon number of 6 to 30, particularly at least one linear alkyl group or linear alkenyl group having a carbon number of 6 to 30, such as amine compounds, fatty acid esters, fatty acid amides, fatty acids, aliphatic alcohols, and aliphatic ethers; and molybdenum-based friction modifiers including sulfur-containing molybdenum complexes such as molybdenum dithiocarbamate and molybdenum dithiophosphate, sulfur-free organic molybdenum complexes such as a molybdenum amine complex and a molybdenum-succinimide complex, and molybdenum disulfide. When the component (F) is contained in the lubricant oil composition of the present invention, the content thereof is usually no less than 0.1 mass % and no more than 5 mass % based on the total amount of the lubricant oil composition as 100 mass %.

<Component (G)>

Examples of the anti-wear agent other than the component (F) include: phosphorus compounds described in the above section on the component (E) (not including the metal), and amine salts thereof; phosphorus compounds such as (mono-, di-, tri-thio)phosphorous acid/phosphoric acid triesters, (mono-, di-thio)phosphonic acid diesters, β-(mono, di) (thio) phosphorylised carboxylic acids; and sulfur-containing compounds such as disulfides, sulfurized olefins, sulfurized oils and fats, and dithiocarbamates. When the component (G) is contained in the lubricant oil composition of the present invention, the content thereof may be usually no less than 0.005 mass % and no more than 5 mass % based on the total amount of the lubricant oil composition as 100 mass %.

<Component (H)>

Examples of the metallic detergent include: alkali metal sulfonates, alkaline earth metal sulfonates, alkali metal phenates, alkaline earth metal phenates, alkali metal salicylates, alkaline earth metal salicylates, and mixtures thereof.

The alkali metal or alkaline earth metal sulfonates, the alkali metal or alkaline earth metal phenates, and the alkali metal or alkaline earth metal salicylates include neutral salts (normal salts) obtained by reacting alkyl aromatic sulfonic acids, alkylphenols, alkylphenol sulfides, Mannich reaction products of alkylphenols, alkylsalicylic acids, etc. directly with metal bases such as oxides and hydroxides of alkali metals or alkaline earth metals, or by once turning them into alkali metal salts such as sodium salts and potassium salts and then substituting them with alkaline earth metal salts (counter cation exchange). They also include: basic salts obtained by heating the neutral salts (normal salts) and an excessive amount of alkali metal salts, alkaline earth metal salts, alkali metal bases, or alkaline earth metal bases (hydroxides or oxides of alkali metals or alkaline earth metals) in the presence of water; and overbased salts (ultrabasic salts) obtained by reacting the neutral salts (normal salts) with bases such as hydroxides of alkali metals or alkaline earth metals in the presence of carbon dioxide, boric acid, or borate. These reactions are usually carried out in a solvent (an aliphatic hydrocarbon solvent such as hexane, an aromatic hydrocarbon solvent such as xylene, a light lubricant base oil, etc.)

Metallic detergents are usually commercially available in the form of being diluted with a light lubricant base oil or the like. In general, a metallic detergent preferably used in the lubricant oil composition of the present invention is the one that has a metal content of preferably no less than 1.0 mass % and more preferably no less than 2.0 mass %, and preferably no more than 20 mass % and more preferably no more than 16 mass %. The base number of the metallic detergent is usually no less than 0 mgKOH/g and preferably no less than 20 mgKOH/g, and usually no more than 500 mgKOH/g and preferably no more than 450 mg KOH/g. Herein, the term “base number” means a base number measured by the perchloric acid method in accordance with Section 7 of JIS K2501 “Petroleum Products and Lubricants-Determination of Neutralization Number”.

In the present invention, one selected from the alkali metal or alkaline earth metal sulfonates, phenates, salicylates, etc. may be used alone, or two or more selected from these may be used in combination. In the present invention, the alkali metal or alkaline earth metal salicylates are especially preferred in that they can contribute to a larger friction reduction effect and a better long-drain performance.

When the component (H) is contained in the lubricant oil composition of the present invention, the content thereof is not particularly limited. When the lubricant oil composition is used for internal combustion engines, the content of the component (H) based on the total amount of the lubricant oil composition is usually no less than 0.01 mass % and no more than mass % in terms of a metal element. At this time, it is preferable to adjust the content of the component (H) with the other additives so that a sulfated ash content of the lubricant oil composition is no more than 1.0 mass %. In such a viewpoint, the upper limit of the content of the metallic detergent based on the total amount (100 mass %) of the lubricant oil composition is preferably 0.3 mass % and more preferably 0.2 mass % in terms of a metal element. In addition, the lower limit thereof is preferably 0.02 mass % and more preferably 0.05 mass %. Herein, the sulfated ash content represents a value measured by the method specified in “Determination of Sulfated Ash” of Section 5 of JIS K 2272, and is mainly derived from a metal-containing additive.

<Component (I)>

Specific examples of the viscosity index improver include: so-called non-dispersant viscosity index improvers such as a polymer of one monomer or a copolymer of two or more monomers selected from various methacrylic acid esters, or hydrogenated products thereof; so-called dispersant viscosity index improvers made by copolymerizing various methacrylic acid esters containing a nitrogen compound; non-dispersant or dispersant ethylene-α-olefin copolymers (examples of α-olefin being propylene, 1-butene, and 1-pentene), or hydrogenated products thereof; polyisobutylene or hydrogenated products thereof; hydrogenated products of styrene-diene copolymers; styrene-maleic anhydride ester copolymers; and polyalkylstyrenes.

The molecular weight of the viscosity index improver needs to be determined in consideration of the shear stability. Specifically, in the case of the dispersant and non-dispersant polymethacrylate for example, the weight-average molecular weight of the viscosity index improver is usually no less than 5,000 and no more than 1,000,000. For lubricant oil compositions employed for the cases where a strong shear force is applied, such as lubricant oil compositions for automatic transmissions, the average molecular weight of the viscosity index improver is preferably no less than 10,000, and preferably no more than 200,000, more preferably no more than 100,000, still more preferably no more than 50,000, and especially preferably no more than 30,000. For lubricant oil compositions for internal combustion engines, the upper limit of the average molecular weight of the viscosity index improver is preferably no more than 800,000, more preferably no more than 500,000, and especially preferably no more than 200,000. When polyisobutylene or a hydrogenated product thereof, which are mainly employed for internal combustion engines is used, the number-average molecular weight thereof is usually no less than 800 and preferably no less than 1,000, and usually no more than 5,000 and preferably no more than 4,000. When an ethylene-α-olefin copolymer or a hydrogenated product thereof is used, the number average molecular weight is usually no less than 800 and preferably no less than 3,000, and usually no more than 500,000 and preferably no more than 200,000.

The use of the ethylene-α-olefin copolymer or the hydrogenated product thereof among the viscosity index improvers makes it possible to obtain a lubricant oil composition especially having an excellent shear stability.

Any one or more compound selected from the above viscosity index improvers may be contained in the lubricant oil composition of the present invention in any amount as the component (I). When the component (I) is contained in the lubricant oil composition of the present invention, the content thereof is usually no less than 0.1 mass % and no more than 20 mass %, based on the amount of the lubricant oil composition.

<Component (J)>

Examples of the corrosion inhibitor include benzotriazole-based, tolyltriazole-based, thiadiazole-based, and imidazole-based compounds.

<Component (K)>

Examples of the rust inhibitor include: petroleum sulfonates, alkylbenzene sulfonates, dinonylnaphthalene sulfonates, alkenyl succinic acid esters, and polyalcohol esters.

<Component (L)>

Examples of the anti-emulsifier include: polyalkylene glycol-type nonionic surfactants such as polyoxyethylene alkyl ethers, polyoxyethylene alkyl phenyl ethers, and polyoxyethylene alkyl naphthyl ethers.

<Component (M)>

Examples of the metal deactivator include: imidazoline, pyrimidine derivatives, alkyl thiadiazoles, mercaptobenzothiazole, benzotriazole or derivatives thereof, 1,3,4-thiadiazole polysulfide, 1,3,4-thiadiazolyl-2,5-bis dialkyl dithiocarbamate, 2-(alkyl dithio)benzimidazole, and β-(o-carboxybenzylthio)propionitrile.

<Component (N)>

Examples of the defoaming agent include: silicones, fluorosilicones, and fluoroalkyl ethers.

<Component (O)>

Examples of the coloring agent include azo compounds.

When these additives are contained in the lubricant oil composition of the present invention, the content of each of (J) the corrosion inhibitor, (K) the rust inhibitor, and (L) the anti-emulsifier based on the total amount of the lubricant oil composition is usually no less than 0.005 mass % and no more than 5 mass %, the content of (M) the metal deactivator based on the total amount of the lubricant oil composition is usually no less than 0.005 mass % and no more than 1 mass %, and the content of (N) the defoaming agent based on the total amount of the lubricant oil composition is usually no less than 0.0005 mass % and no more than 1 mass %.

The lubricant oil composition of the present invention contains an oiliness agent-type friction modifier, and can exhibit a better friction reduction effect than lubricant oil compositions containing a conventional oiliness agent-type friction modifier under a wider range of friction conditions. The anti-wear properties can also be improved. Therefore, the lubricant oil composition of the present invention can be favorably used to lubricate internal combustion engines. That is, by using the lubricant oil composition of the present invention to lubricate internal combustion engines, it is not only possible to effectively reduce the energy loss by friction in the internal combustion engines under a wider range of operating conditions and improve fuel efficiency, but also possible to effectively protect components of the internal combustion engines against wear under a wider range of operating conditions.

While a valve train system in the internal combustion engines is one of the devices that operates under the most severe conditions in terms of friction and wear, the lubricant oil composition of the present invention exhibits high friction reduction effect and anti-wear properties as described above. Therefore, the lubricant oil composition of the present invention can be favorably employed to lubricate internal combustion engines having a direct acting-type or roller follower-type valve train system, especially internal combustion engines having a roller follower-type valve train system.

Since the lubricant oil composition of the present invention contains an oiliness agent-type friction modifier with no sulfur or phosphorus content, using the lubricant oil composition of the present invention to lubricate internal combustion engines can reduce burden on an exhaust-gas aftertreatment device. Therefore, the lubricant oil composition of the present invention can be favorably employed to lubricate internal combustion engines equipped with the exhaust-gas aftertreatment device. It can also be especially favorably employed to lubricate internal combustion engines that use, as a fuel, a low-sulfur fuel such as gasoline, light oil, and kerosene having a sulfur content of no more than 50 mass ppm, preferably no more than 30 mass ppm, and especially preferably no more than 10 mass ppm, and a fuel having a sulfur content of no more than 1 mass ppm (liquefied petroleum gas (LPG), natural gas, hydrogen substantially not containing sulfur, dimethyl ether, an alcohol, GTL (gas-to-liquid) fuel, etc.)

Since the boron component in the borate ester compound can be regarded as an ash component, the ash component derived from the boron component is seen to affect an exhaust-gas purifying device of the internal combustion engines to some extent when the lubricant oil composition of the present invention is used to lubricate the internal combustion engine. As for the molybdenum-based FM, since MoDTC contains sulfur and MoDTP contains sulfur and phosphorus in addition to an ash component derived from molybdenum, these components negatively affect the exhaust gas purifier in combination or synergistically. On the other hand, the components (A) and (B) in the present invention do not contain metal components such as molybdenum, and also do not contain sulfur or phosphorus. Therefore, by using the lubricant oil composition of the present invention to lubricate internal combustion engines, it is possible to easily reduce the burden on the exhaust gas purifier compared with the case of using lubricant oil compositions containing the molybdenum-based FM.

The lubricant oil composition of the present invention can also be favorably used to lubricate automatic transmissions. That is, using the lubricant oil composition of the present invention to lubricate automatic transmissions allows effective control of operations of the automatic transmissions under a wide variety of operating conditions, such as reducing the shock upon clutch engagement and preventing shudder in slippage control.

In the above descriptions on the present invention, the uses of the lubricant oil composition of the present invention for lubricating internal combustion engines and for lubricating automatic transmissions have been shown; however, the lubricant oil composition of the present invention is not limited to such uses. Since the lubricant oil composition of the present invention has an excellent friction reduction effect as described above, it can also be favorably employed as a lubricant oil required to show low-friction characteristics, for example as a lubricant oil for manual transmissions etc. and a lubricant oil such as grease, wet brake oil, hydraulic oil, turbine oil, compressor oil, bearing oil, and refrigerator oil.

EXAMPLES

Hereinafter, the present invention will be described in more detail based on Examples and Comparative Examples. It should be noted that the present invention is not limited to the Examples.

Examples 1 to 3, and Comparative Examples 1 to 6

As shown in Table 1, the lubricant oil compositions of the present invention (Examples 1 to 3) and the lubricant oil compositions for comparison (Comparative Examples 1 to 6) were prepared.

TABLE 1 Compar- Compar- Compar- Compar- Compar- Compar- ative ative ative ative ative ative Example Example Example Example Example Example Example Example Example 1 2 3 1 2 3 4 5 6 base oil PAO2 mass % Balance Balance Balance Balance Balance Balance Balance Balance Balance component (A) oleyl urea mass % 0.27  1.1   — 0.27  — — 1.1  — — (in terms of nitrogen) mass % (0.024)  (0.10)  — (0.024) — — (0.10) — — component (A) oleyl amide mass % — — 0.24  — 0.24  — — — — (in terms of nitrogen) mass % — — (0.012)  — (0.012) — — — — component (B) tri-n-butyl borate mass % 0.20  0.82  0.20  — — 0.20  — 0.82  — (in terms of boron) mass % (0.0094) (0.039) (0.0094) — — (0.0094) — (0.039) — zinc dialkylthiophosphate mass % — — — — — — — — (0.080) (in terms of phosphorus) molybdenum dithiocarbamate mass % — — — — — — — — (0.050) (in terms of molybdenum) molar ratio 1.0   1.0  1.0   — — — — — — (component (B) in terms boron/ component (A))

Example 1

A lubricant oil composition was prepared, which contained: 0.27 mass % of oleyl urea (in the general formula (1), m=1, n=0, R¹=oleyl group (C18), R²═R³═R⁴═H) as the component (A); 0.20 mass (0.0094 mass % in terms of boron) of tributyl borate (in the general formula (2), R⁵═R⁶═R′=butyl group) as the component (B); and a lubricant base oil PAO2 as the remainder. The molar ratio (B/A) between the molar content of the component (A) and the molar content of the component (B) in terms of boron was 1.0 (Table 1).

Example 2

A lubricant oil composition was prepared in the same manner as in Example 1, except that the content of the component (A) and the content of the component (B) was 1.1 mass % and 0.82 mass %, respectively (Table 1).

Example 3

A lubricant oil composition was prepared, which contained: 0.24 mass % of oleyl amide (in the general formula (1), m=0, R¹═C₁₇H₃₃ group, R²═R³═R⁴═H) as the component (A); 0.20 mass % (0.0094 mass % in terms of boron) of tri-n-butyl borate (in the general formula (2), R⁵═R⁶═R⁷=n-butyl group) as the component (B); and a lubricant base oil PAO2 as the remainder. The molar ratio (B/A) between the molar content of the component (A) and the molar content of the component (B) in terms of boron was 1.0 (Table 1).

Comparative Example 1

A lubricant oil composition was prepared in the same manner as in Example 1, except that the component (B) was not contained (Table 1).

Comparative Example 2

A lubricant oil composition was prepared in the same manner as in Example 3, except that the component (B) was not contained (Table 1).

Comparative Example 3

A lubricant oil composition was prepared in the same manner as in Example 1, except that the component (A) was not contained (Table 1).

Comparative Example 4

A lubricant oil composition was prepared in the same manner as in Example 2, except that the component (B) was not contained (Table 1).

Comparative Example 5

A lubricant oil composition was prepared in the same manner as in Example 2, except that the component (A) was not contained (Table 1).

Comparative Example 6

A lubricant oil composition of Comparative Example 6 contained a molybdenum-based friction modifier instead of an oiliness agent-type friction modifier. The lubricant oil composition was prepared in the same manner as in Example 1, except that it did not contain the component (A) nor the component (B) but contained 0.080 mass % of zinc dialkyl dithiophosphate (ZnDTP) in terms of phosphorus content and 0.050 mass % of molybdenum dithiocarbamate (MoDTC) in terms of molybdenum content.

(Evaluation Method)

A ball-on-disc friction test was conducted for each of the lubricant oil compositions prepared above. After a running-in operation was carried out at a frequency of 50 Hz for a certain period under the conditions of a temperature of 100° C., a load of 20 N, and an amplitude of 1 mm, friction coefficients were measured while reducing the frequency to 40 Hz, 30 Hz, 20 Hz, 10 Hz, 5 Hz, 3 Hz, and 2 Hz, in the mentioned order.

FIGS. 1 to 3 show graphs plotted for each of the lubricant oil compositions, taking the frequency on the horizontal axis and the friction coefficient on the vertical axis.

(Evaluation Results)

FIG. 1 is a graph comparing the test result of Example 1 with the test results of Comparative Examples 1, 3, and 6.

As shown in FIG. 1, the lubricant oil composition of Example 1 showed an excellent friction reduction effect stably in the whole range of frequencies tested. It is especially noteworthy that it showed a better friction reduction effect constantly than the lubricant oil composition of Comparative Example 6 which contained the molybdenum-based friction modifier.

The friction reduction effect of the lubricant oil composition of Comparative Example 1 which did not contain the component (B) was inferior to that of Example 1 in almost the whole range of frequencies tested. Further, as a result of the large variation of the friction reduction effect in association with the frequency, the friction reduction effect in the range of relatively low frequencies was inferior to that of Comparative Example 6 which contained the molybdenum-based friction modifier.

The friction reduction effect of the lubricant oil composition of Comparative Example 3 which did not contain the component (A) was significantly poor compared with that of Example 1 and also those of Comparative Examples 1 and 6.

FIG. 2 is a graph comparing the test result of Example 3 with the test results of Comparative Examples 2, 3, and 6.

As shown in FIG. 2, the lubricant oil composition of Example 3 showed an excellent friction reduction effect stably in the whole range of frequencies tested. It is especially noteworthy that it showed a better friction reduction effect constantly than the lubricant oil composition of Comparative Example 6 which contained the molybdenum-based friction modifier.

The friction reduction effect of the lubricant oil composition of Comparative Example 2 which did not contain the component (B) was inferior to those of Example 3 and Comparative Example 6 in the whole range of frequencies tested.

The friction reduction effect of the lubricant oil composition of Comparative Example 3 which did not contain the component (A) was significantly poor compared with that of Example 3 and also those of Comparative Examples 2 and 6.

FIG. 3 is a graph comparing the test result of Example 2 with the test results of Comparative Examples 4, 5, and 6.

As shown in FIG. 3, the lubricant oil composition of Example 2 showed an excellent friction reduction effect stably in the whole range of frequencies tested. It is especially noteworthy that it showed a better friction reduction effect constantly than the lubricant oil composition of Comparative Example 6 which contained the molybdenum-based friction modifier.

The friction reduction effect of the lubricant oil composition of Comparative Example 4 which did not contain the component (B) was inferior to that of Example 2 in most of the range of frequencies tested. Further, as a result of the large variation of the friction reduction effect in association with the frequency, the friction reduction effect in the range of relatively low frequencies was inferior to that of Comparative Example 6 which contained the molybdenum-based friction modifier.

The friction reduction effect of the lubricant oil composition of Comparative Example 5 which did not contain the component (A) was significantly poor compared with that of Example 2 and also those of Comparative Examples 4 and 6.

The above test results show that the present invention can provide a lubricant oil composition containing an oiliness agent-type friction modifier that can exhibit a better friction reduction effect under a wider range of friction conditions, than lubricant oil compositions containing a conventional oiliness agent-type friction modifier.

Examples 1, 4, and 5, and Comparative Example 1

In addition to the lubricant oil compositions of Example 1 and Comparative Example 1 above, two more lubricant oil compositions of the present invention (Examples 4 and 5) were prepared, as shown in Table 2.

TABLE 2 Comparative Example 1 Example 4 Example 5 Example 1 base oil PAO2 mass % Balance Balance Balance Balance component (A) oleyl urea mass % 0.27 0.27 0.27 0.27 (in terms of nitrogen) mass % (0.024) (0.024) (0.024) (0.024) component (B) tri-n-butyl borate mass % 0.20 — — — (in terms of boron) mass % (0.0094) — — — component (B) tri-n-octyl borate mass % — 0.35 — — (in terms of boron) mass % — (0.0094) — — component (B) tri-n-octadecyl borate mass % — — 0.71 — (in terms of boron) mass % — — (0.0094) — molar ratio 1.0 1.0 1.0 — (component (B) in terms of boron/component (A))

Example 4

A lubricant oil composition was prepared in the same manner as in Example 1, except that the component (B) was tri-n-octyl borate (in the general formula (2), R⁵═R⁶═R⁷=n-octyl group) (Table 2). The content of the component (B) was 0.0094 mass % in terms of boron content, which was the same as in Example 1.

Example 5

A lubricant oil composition was prepared in the same manner as in Example 1, except that the component (B) was tri-n-octadecyl borate (in the general formula (2), R⁵═R⁶═R⁷=n-octadecyl group) (Table 2). The content of the component (B) was 0.0094 mass % in terms of boron content, which was the same as in Example 1.

(Evaluation Method)

A ball-on-disc friction test was conducted in the same manner as above. The results are shown in FIG. 4.

(Evaluation Results)

FIG. 4 is a graph comparing the test results of Examples 1, 4, and 5 with the test result of Comparative Example 1.

As shown in FIG. 4, even when the compounds of the component (B) in Examples 4 and 5 were used instead, the friction reduction effects of Examples 4 and 5 were as excellent as that of Example 1.

Examples 1, and 6 to 8

In addition to the lubricant oil composition of Example 1 described above, three more lubricant oil composition of the present invention (Examples 6 to 8) were prepared as shown in Table 3.

TABLE 3 Example 6 Example 1 Example 7 Example 8 base oil PAO2 mass % Balance Balance Balance Balance component (A) oleyl urea mass % 0.27 0.27 0.27 0.27 (in terms of nitrogen) mass % (0.024) (0.024) (0.024) (0.024) component (B) tri-n-butyl borate mass % 0.10 0.20 0.40 0.80 (in terms of boron) mass % (0.0047) (0.0094) (0.019) (0.038) molar ratio 0.5 1.0 2.0 4.0 (component (B) in terms of boron/component (A))

Example 6

A lubricant oil composition was prepared in the same manner as in Example 1, except that the content of the component (B) was changed so that the molar ratio (B/A) between the molar content of the component (A) and the molar content of the component (B) in terms of boron was 0.5 (Table 3).

Example 7

A lubricant oil composition was prepared in the same manner as in Example 1, except that the content of the component (B) was changed so that the molar ratio (B/A) between the molar content of the component (A) and the molar content of the component (B) in terms of boron was 2.0 (Table 3).

Example 8

A lubricant oil composition was prepared in the same manner as in Example 1, except that the content of the component (B) was changed so that the molar ratio (B/A) between the molar content of the component (A) and the molar content of the component (B) in terms of boron was 4.0 (Table 3).

(Evaluation Method)

A ball-on-disc test friction test was conducted in the same manner as described above. The results are shown in FIG. 5.

(Evaluation Results)

FIG. 5 is a graph showing the test results of Examples 1, and 6 to 8.

As shown in FIG. 5, the lubricant oil compositions of Examples 1, 6, and 7 having a preferable range of the molar ratio (B/A) between the component (A) and the component (B) exhibited an excellent friction reduction effect stably in the whole range of frequencies tested.

The lubricant oil composition of Example 8 exhibited an excellent friction reduction effect in the range of relatively low frequencies.

The above test results show that the lubricant oil composition of the present invention can exhibit a favorable friction reduction even when the molar ratio (B/A) between the molar content of the component (A) and the molar content of the component (B) in terms of boron is changed.

The present invention has been described above as to the embodiment (s) which is (are) supposed to be practical as well as preferable at present. However, it should be understood that the present invention is not limited to the embodiment(s) disclosed in the specification and can be appropriately modified within the range that does not depart from the gist or spirit of the invention, which can be read from the appended claims and the overall specification, and that a lubricant additive and a lubricant oil composition with such modifications are also encompassed within the technical range of the invention.

INDUSTRIAL APPLICABILITY

The lubricant additive and the lubricant oil composition of the present invention can be favorably used to lubricate various devices and can be favorably used especially for lubrication of internal combustion engines and automatic transmissions. 

1. A lubricant additive comprising: (A) a nitrogen-containing compound represented by the general formula (1); and (B) a borate ester compound represented by the general formula (2) and/or a borate ester compound represented by the general formula (3):

wherein, for general formula (1), R¹ represents a hydrocarbyl group having a carbon number of 1 to 30 or a functionalized hydrocarbyl group having a carbon number of 1 to 30; each of R², R³, and R⁴ independently represents a hydrocarbyl group having a carbon number of 1 to 30, a functionalized hydrocarbyl group having a carbon number of 1 to 30, or a hydrogen atom; m represents an integer of 0 or 1; and n represents an integer of 0 or 1 where m is 1;

for general formula (2), R⁵ represents a hydrocarbyl group having a carbon number of 1 to 30 or a functionalized hydrocarbyl group having a carbon number of 1 to 30; and each of R⁶ and R⁷ independently represents a hydrocarbyl group having a carbon number of 1 to 30, a functionalized hydrocarbyl group having a carbon number of 1 to 30, or a hydrogen atom;

for general formula (3), R⁸ represents a hydrocarbyl group having a carbon number of 1 to 30 or a functionalized hydrocarbyl group having a carbon number of 1 to 30; and each of R⁹ and R¹⁹ independently represents a hydrocarbyl group having a carbon number of 1 to 30, a functionalized hydrocarbyl group having a carbon number of 1 to 30, or a hydrogen atom.
 2. The lubricant additive according to claim 1, wherein a molar ratio of the molar content of the component (B) in terms of boron to the molar content of the component (A) is 0.05 to 4.0.
 3. The lubricant additive according to claim 1, further comprising: one or more selected from the group consisting of: a lubricant base oil, an ashless dispersant, an antioxidant, a friction modifier, an anti-wear agent, a metallic detergent, a viscosity index improver, a corrosion inhibitor, an anti-rust agent, an anti-emulsifier, a metal deactivator, a defoaming agent, and a coloring agent.
 4. A lubricant oil composition comprising: a lubricant base oil; and the lubricant additive according to claim
 1. 